diff --git a/client.go b/client.go
index fe44c8a..9825f03 100644
--- a/client.go
+++ b/client.go
@@ -42,7 +42,7 @@ func NewClient(config ClientConfig) (*Client, error) {
 		tlsHandshake: config.TLSHandshake,
 		logger:       config.Logger,
 	}
-	if !client.server.IsValid() || client.dialer == nil || client.tlsHandshake == nil {
+	if !client.server.IsValid() || client.dialer == nil {
 		return nil, os.ErrInvalid
 	}
 	switch client.version {
@@ -56,11 +56,18 @@ func NewClient(config ClientConfig) (*Client, error) {
 	return client, nil
 }
 
+func (c *Client) SetHandshakeFunc(handshakeFunc TLSHandshakeFunc) {
+	c.tlsHandshake = handshakeFunc
+}
+
 func (c *Client) DialContext(ctx context.Context) (net.Conn, error) {
 	conn, err := c.dialer.DialContext(ctx, N.NetworkTCP, c.server)
 	if err != nil {
 		return nil, err
 	}
+	if c.tlsHandshake == nil {
+		return nil, os.ErrInvalid
+	}
 	switch c.version {
 	default:
 		fallthrough